[RFC PATCH v2 1/4] arm64: defconfig: increase NR_CPUS range to 2-128

Arnd Bergmann
2014-12-09T08:27:13Z

On Monday 08 December 2014 17:57:03 Zi Shen Lim wrote:
> Hi Arnd,
>
> On Mon, Nov 24, 2014 at 3:53 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> >
> > On Saturday 22 November 2014 02:53:27 Ganapatrao Kulkarni wrote:
> > > Raising the maximum limit to 128. This is needed for Cavium's
> > > Thunder system that will have 96 cores on Multi-node system.
> > >
> > > Signed-off-by: Ganapatrao Kulkarni <ganapatrao.kulkarni@caviumnetworks.com>
> > >
> >
> > Could we please raise the compile-time limit to the highest number that
> > you are able to boot successfully on some existing machine?
> >
> > There isn't much point in doubling this every few months.
>
> Agreed. If we look back at [1], Mark Rutland has actually compiled and
> boot-tested NR_CPUS=4096 on Juno.
>
> [1] https://lkml.org/lkml/2014/9/8/537

Ok, 4096 sounds like a good NR_CPUS limit then, it should last for a while.

For the defconfig, we probably want a much smaller value, either one that
covers all known machines (96 at this time), or something that covers
95% of all users (maybe 32?) and does not have an serious impact on
memory consumption or performance on small machines.

Arnd